Lei Chang

Bio: Lei Chang is an academic researcher from Nanjing Medical University. The author has contributed to research in topics: Neuroprotection & Stroke. The author has an hindex of 14, co-authored 37 publications receiving 592 citations.

Hippocampal Neuronal Nitric Oxide Synthase Mediates the Stress-Related Depressive Behaviors of Glucocorticoids by Downregulating Glucocorticoid Receptor

Abstract: The molecular mechanisms underlying the behavioral effects of glucocorticoids are poorly understood. We report here that hippocampal neuronal nitric oxide synthase (nNOS) is a crucial mediator. Chronic mild stress and glucocorticoids exposures caused hippocampal nNOS overexpression via activating mineralocorticoid receptor. In turn, hippocampal nNOS-derived nitric oxide (NO) significantly downregulated local glucocorticoid receptor expression through both soluble guanylate cyclase (sGC)/cGMP and peroxynitrite (ONOO(-))/extracellular signal-regulated kinase signal pathways, and therefore elevated hypothalamic corticotrophin-releasing factor, a peptide that governs the hypothalamic-pituitary-adrenal axis. More importantly, nNOS deletion or intrahippocampal nNOS inhibition and NO-cGMP signaling blockade (using NO scavenger or sGC inhibitor) prevented the corticosterone-induced behavioral modifications, suggesting that hippocampal nNOS is necessary for the role of glucocorticoids in mediating depressive behaviors. In addition, directly delivering ONOO(-) donor into hippocampus caused depressive-like behaviors. Our findings reveal a role of hippocampal nNOS in regulating the behavioral effects of glucocorticoids.

CAPON-nNOS coupling can serve as a target for developing new anxiolytics

Abstract: Anxiety disorders are highly prevalent psychiatric diseases. There is need for a deeper understanding of anxiety control mechanisms in the mammalian brain and for development of new anxiolytic agents. Here we report that the coupling between neuronal nitric oxide synthase (nNOS) and its carboxy-terminal PDZ ligand (CAPON) can serve as a target for developing new anxiolytic agents. Augmenting nNOS-CAPON interaction in the hippocampus of mice by overexpressing full-length CAPON gave rise to anxiogenic-like behaviors, whereas dissociating CAPON from nNOS by overexpressing CAPON-125C or CAPON-20C (the C-terminal 125 or 20 amino acids of CAPON) or delivering Tat-CAPON-12C (a peptide comprising Tat and the 12 C-terminal amino acids of CAPON) in the hippocampus of mice produced anxiolytic-like effects. Mice subjected to chronic mild stress (CMS) displayed a substantial increase in nNOS-CAPON coupling in the hippocampus and a consequent anxiogenic-like phenotype. Disrupting nNOS-CAPON coupling reversed the CMS-induced anxiogenic-like behaviors. Moreover, small-molecule blockers of nNOS-CAPON binding rapidly produced anxiolytic-like effects. Dexamethasone-induced ras protein 1 (Dexras1)-extracellular signal-regulated kinase (ERK) signaling was involved in the behavioral effects of nNOS-CAPON association. Thus, nNOS-CAPON association contributes to the modulation of anxiety-related behaviors via regulating Dexras1-ERK signaling and can serve as a target for developing potential anxiolytics.

Interaction of nNOS with PSD-95 Negatively Controls Regenerative Repair after Stroke

Abstract: Stroke is a major public health concern. The lack of effective therapies heightens the need for new therapeutic targets. Mammalian brain has the ability to rewire itself to restore lost functionalities. Promoting regenerative repair, including neurogenesis and dendritic remodeling, may offer a new therapeutic strategy for the treatment of stroke. Here, we report that interaction of neuronal nitric oxide synthase (nNOS) with the protein postsynaptic density-95 (PSD-95) negatively controls regenerative repair after stroke in rats. Dissociating nNOS–PSD-95 coupling in neurons promotes neuronal differentiation of neural stem cells (NSCs), facilitates the migration of newborn cells into the injured area, and enhances neurite growth of newborn neurons and dendritic spine formation of mature neurons in the ischemic brain of rats. More importantly, blocking nNOS–PSD-95 binding during the recovery stage improves stroke outcome via the promotion of regenerative repair in rats. Histone deacetylase 2 in NSCs may mediate the role of nNOS–PSD-95 association. Thus, nNOS–PSD-95 can serve as a target for regenerative repair after stroke.

BIdirectional Regulation of Neurogenesis by Neuronal Nitric Oxide Synthase Derived from Neurons and Neural Stem Cells

Abstract: It has been demonstrated that neuronal nitric oxide synthase (nNOS) negatively regulates adult neurogenesis. However, the cellular and molecular mechanisms underlying are poorly understood. Here, we show that nNOS from neural stem cells (NSCs) and from neurons play opposite role in regulating neurogenesis. The NSCs treated with nNOS inhibitor N(5)-(1-imino-3-butenyl)-L- ornithine (L-VNIO) or nNOS gene deletion exhibited significantly decreased proliferation and neuronal differentiation, indicating that NSCs-derived nNOS is essential for neurogenesis. The NSCs cocultured with neurons displayed a significantly decreased proliferation, and deleting nNOS gene in neurons or scavenging extracellular nitric oxide (NO) abolished the effects of coculture, suggesting that neurons-derived nNOS, a source of exogenous NO for NSCs, exerts a negative control on neurogenesis. Indeed, the NSCs exposed to NO donor DETA/NONOate displayed decreased proliferation and neuronal differentiation. The bidirectional regulation of neurogenesis by NSCs- and neurons-derived nNOS is probably related to their distinct subcellular localizations, mainly in nuclei for NSCs and in cytoplasm for neurons. Both L-VNIO and DETA/NONOate inhibited telomerase activity and proliferation in wild-type (WT) but not in nNOS(-/-) NSCs, suggesting a nNOS-telomerase signaling in neurogenesis. The NSCs exposed to DETA/NONOate exhibited reduced cAMP response element binding protein (CREB) phosphorylation, nNOS expression, and proliferation. The effects of DETA/NONOate were reversed by forskolin, an activator of CREB signaling. Moreover, disrupting CREB phosphorylation by H-89 or LV-CREB133-GFP simulated the effects of DETA/NONOate, and inhibited telomerase activity. Thus, we conclude that NSCs-derived nNOS stimulates neurogenesis via activating telomerase, whereas neurons-derived nNOS represses neurogenesis by supplying exogenous NO that hinders CREB activation, in turn, reduces nNOS expression in NSCs.

Opening a New Time Window for Treatment of Stroke by Targeting HDAC2

Abstract: Narrow therapeutic window limits treatments with thrombolysis and neuroprotection for most stroke patients. Widening therapeutic window remains a critical challenge. Understanding the key mechanisms underlying the pathophysiological events in the peri-infarct area where secondary injury coexists with neuroplasticity over days to weeks may offer an opportunity for expanding the therapeutic window. Here we show that ischemia-induced histone deacetylase 2 (HDAC2) upregulation from 5 to 7 d after stroke plays a crucial role. In this window phase, suppressing HDAC2 in the peri-infarct cortex of rodents by HDAC inhibitors, knockdown or knock-out of Hdac2 promoted recovery of motor function from stroke via epigenetically enhancing cells survival and neuroplasticity of surviving neurons as well as reducing neuroinflammation, whereas overexpressing HDAC2 worsened stroke-induced functional impairment of both WT and Hdac2 conditional knock-out mice. More importantly, inhibiting other isoforms of HDACs had no effect. Thus, the intervention by precisely targeting HDAC2 in this window phase is a novel strategy for the functional recovery of stroke survivors.SIGNIFICANCE STATEMENT Narrow time window phase impedes current therapies for stroke patients. Understanding the key mechanisms underlying secondary injury may open a new window for pharmacological interventions to promote recovery from stroke. Our study indicates that ischemia-induced histone deacetylase 2 upregulation from 5 to 7 d after stroke mediates the secondary functional loss by reducing survival and neuroplasticity of peri-infarct neurons as well as augmenting neuroinflammation. Thus, precisely targeting histone deacetylase 2 in the window phase provides a novel therapeutic strategy for stroke recovery.

Neuroinflammation: friend and foe for ischemic stroke

Abstract: Stroke, the third leading cause of death and disability worldwide, is undergoing a change in perspective with the emergence of new ideas on neurodegeneration The concept that stroke is a disorder solely of blood vessels has been expanded to include the effects of a detrimental interaction between glia, neurons, vascular cells, and matrix components, which is collectively referred to as the neurovascular unit Following the acute stroke, the majority of which are ischemic, there is secondary neuroinflammation that both promotes further injury, resulting in cell death, but conversely plays a beneficial role, by promoting recovery The proinflammatory signals from immune mediators rapidly activate resident cells and influence infiltration of a wide range of inflammatory cells (neutrophils, monocytes/macrophages, different subtypes of T cells, and other inflammatory cells) into the ischemic region exacerbating brain damage In this review, we discuss how neuroinflammation has both beneficial as well as detrimental roles and recent therapeutic strategies to combat pathological responses Here, we also focus on time-dependent entry of immune cells to the ischemic area and the impact of other pathological mediators, including oxidative stress, excitotoxicity, matrix metalloproteinases (MMPs), high-mobility group box 1 (HMGB1), arachidonic acid metabolites, mitogen-activated protein kinase (MAPK), and post-translational modifications that could potentially perpetuate ischemic brain damage after the acute injury Understanding the time-dependent role of inflammatory factors could help in developing new diagnostic, prognostic, and therapeutic neuroprotective strategies for post-stroke inflammation

Sucrose preference test for measurement of stress-induced anhedonia in mice

Abstract: Anhedonia is the inability to experience pleasure from rewarding or enjoyable activities and is a core symptom of depression in humans. Here, we describe a protocol for the measurement of anhedonia in mice, in which anhedonia is measured by a sucrose preference test (SPT) based on a two-bottle choice paradigm. A reduction in the sucrose preference ratio in experimental relative to control mice is indicative of anhedonia. To date, inconsistent and variable results have been reported following the use of the SPT by different groups, probably due to the use of different protocols and equipment. In this protocol, we describe how to set up a clearly defined apparatus for SPT and provide a detailed protocol to ensure greater consistency when carrying out SPT. This optimized protocol is highly sensitive, reliable, and adaptable for evaluation of chronic stress-related anhedonia, as well as morphine-induced dependence. The whole SPT, including adaptation, baseline measurement, and testing, takes 8 d.

Synaptic plasticity in depression: molecular, cellular and functional correlates.

Abstract: Synaptic plasticity confers environmental adaptability through modification of the connectivity between neurons and neuronal circuits. This is achieved through changes to synapse-associated signaling systems and supported by complementary changes to cellular morphology and metabolism within the tripartite synapse. Mounting evidence suggests region-specific changes to synaptic form and function occur as a result of chronic stress and in depression. Within subregions of the prefrontal cortex (PFC) and hippocampus structural and synapse-related findings seem consistent with a deficit in long-term potentiation (LTP) and facilitation of long-term depression (LTD), particularly at excitatory pyramidal synapses. Other brain regions are less well-studied; however the amygdala may feature a somewhat opposite synaptic pathology including reduced inhibitory tone. Changes to synaptic plasticity in stress and depression may correlate those to several signal transduction pathways (e.g. NOS-NO, cAMP-PKA, Ras-ERK, PI3K-Akt, GSK-3, mTOR and CREB) and upstream receptors (e.g. NMDAR, TrkB and p75NTR). Deficits in synaptic plasticity may further correlate disrupted brain redox and bioenergetics. Finally, at a functional level region-specific changes to synaptic plasticity in depression may relate to maladapted neurocircuitry and parallel reduced cognitive control over negative emotion.

The microRNA cluster miR-106b~25 regulates adult neural stem/progenitor cell proliferation and neuronal differentiation.

Abstract: In adult mammals, neural stem cells (NSCs) generate new neurons that are important for specific types of learning and memory. Controlling adult NSC number and function is fundamental for preserving the stem cell pool and ensuring proper levels of neurogenesis throughout life. Here we study the importance of the microRNA gene cluster miR-106b~25 (miR-106b, miR-93, and miR-25) in primary cultures of neural stem/progenitor cells (NSPCs) isolated from adult mice. We find that knocking down miR-25 decreases NSPC proliferation, whereas ectopically expressing miR-25 promotes NSPC proliferation. Expressing the entire miR-106b~25 cluster in NSPCs also increases their ability to generate new neurons. Interestingly, miR-25 has a number of potential target mRNAs involved in insulin/insulin-like growth factor-1 (IGF) signaling, a pathway implicated in aging. Furthermore, the regulatory region of miR-106b~25 is bound by FoxO3, a member of the FoxO family of transcription factors that maintains adult stem cells and extends lifespan downstream of insulin/IGF signaling. These results suggest that miR-106b~25 regulates NSPC function and is part of a network involving the insulin/IGF-FoxO pathway, which may have important implications for the homeostasis of the NSC pool during aging.

Amygdalar neural ensemble that encodes the unpleasantness of pain

Abstract: An ensemble of neurons in the basolateral amygdala (BLA) has been identified that encodes nociceptive information across pain modalities, including pain evoked by noxious thermal and mechanical stimuli. Methods are provided for screening candidate agents for inhibition of neural activity of the BLA nociceptive ensemble. Screening assays further include determining the effectiveness of candidate agents in alleviating pain and reducing aversive pain avoidance behavior.